1. Field of the Invention
This invention relates to electrochemical devices and to methods of making them. More particularly, this invention is directed to a novel multicell electrochemical device having a plurality of bipolar carbon-plastic electrode structures and a novel method of making the device.
Numerous configurations for electrochemical devices have been developed over the years along with particular methods of making these devices to satisfy various electrical requirements and physical limitations on systems which use the devices. Recently, the need for more efficient automobile and vehicular battery and power systems has become apparent. The long used conventional lead/acid battery has become the object of much modification and development. Thus, for example, a new generation of lead/acid "life of the car", maintenance-free batteries has emerged. Nonetheless, in this era of energy conservation, of trimming the weight from conventional vehicles, of developing high energy density cell electric vehicles, and of using both novel means and conventional means to produce and to store energy in efficient manners, the need for an easily fabricated, lightweight multicell electrochemical device has become acute. The present invention is directed to satisfying this need.
2. Description of the Prior Art
In the past, the development of electrode structures for electrochemical cells involved the use of plastic for some parts of the electrodes, and this was, at least in part, successful. For example, U.S. Pat. No. 2,496,709 (Gelardin) describes a duplex electrode formed of a metal plate with various types of plastic and carbon plastic coatings thereon, around which a plastic frame is injection molded. Electrolyte compositions and other materials are added and stacks of these composited duplex electrodes are snapped together in a locking interengagement. Unfortunately, the reference discloses devices and techniques involving the use of heavy, expensive metal plates in the electrodes. U.S. Pat. No. 3,901,731 (Warszawski et al.), and the patents cited therein describe forming a framed electrode by molding a plastic frame around a preformed electrode. U.S. Pat. Nos. 2,416,576 (Franz et al.) and 2,966,538 (Bernot) describe stacked components of cells enclosed in plastic cups forming frame-like structures wherein the plastic parts may be sealed by heat welding or high frequency welding. However, these devices involve the stacking of a number of layers, including electrolyte and zinc metal anode, prior to fabrication and sealing of the finished cup structure. U.S. Pat. No. 3,775,189 (Jaggard) discloses the fabrication of an electrochemical cell involving the use of plastics, heat welding, and ultrasonic welding, including encapsulation of edges of certain electrode structures. The patent also teaches the use of melt beads or protusions to enhance ultrasonic welding. However, this patent is directed to the formation of single cells and bicells (cells having one anode and two cathodes), and is not directed to the fabrication of devices having a multiplicity of cells. U.S. Pat. No. 3,941,615 (McDowall) describes a tongue and groove joining means for adjacent plastic elements in a lead-acid battery system and is representative of one state of the art development.
Notwithstanding the many developments in the art of electrochemical device design and fabrication, as represented by the prior art cited above, due to the shortcomings in these developments, the need for easily fabricated, lightweight, multicell electrochemical devices and enhanced fabrication techniques still exists. None of the prior art disclosures teach or suggest the electrochemical device and fabrication technique of the present invention which satisfies this need.